Added Coremongo package

Added Coremongo package

dalmdl/coremongo/girdfs.go

+package coremongo
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"strings"
+	"time"
+
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/gridfs"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+//SaveFileToGridFS - Saves file to gridfs
+func SaveFileToGridFS(db *mongo.Database, bucketName, fileName string, source io.Reader) (string, string, error) {
+
+	bucketName = strings.TrimSpace(bucketName)
+	fileName = strings.TrimSpace(fileName)
+
+	//Validations
+	if db == nil {
+		return "", "", errors.New("db Required")
+	} else if bucketName == "" {
+		return "", "", errors.New("bucketName required")
+	} else if source == nil {
+		return "", "", errors.New("invalid source")
+	}
+
+	//Set bucket config
+	bucketOptions := options.BucketOptions{}
+	bucketOptions.Name = &bucketName
+
+	//Get bucket instance
+	dbBucket, bucketError := gridfs.NewBucket(db, &bucketOptions)
+	if bucketError != nil {
+		return "", "", bucketError
+	}
+
+	//Upload incomming file to bucket
+	fileID, fileError := dbBucket.UploadFromStream(fileName, source)
+	if fileError != nil {
+		return "", "", fileError
+	}
+
+	//Return generated fileId and file name
+	return fileID.String(), fileName, nil
+}
+
+//GetFileFromGridFS - Gets file from gridfs
+func GetFileFromGridFS(db *mongo.Database, bucketName, fileName string) ([]byte, error) {
+
+	bucketName = strings.TrimSpace(bucketName)
+	fileName = strings.TrimSpace(fileName)
+
+	//Validations
+	if db == nil {
+		return nil, errors.New("db Required")
+	} else if bucketName == "" {
+		return nil, errors.New("bucketName required")
+	} else if fileName == "" {
+		return nil, errors.New("fileName required'")
+	}
+
+	//Set bucket config
+	bucketOptions := options.BucketOptions{}
+	bucketOptions.Name = &bucketName
+
+	//Get bucket instance
+	dbBucket, bucketError := gridfs.NewBucket(db, &bucketOptions)
+	if bucketError != nil {
+		return nil, bucketError
+	}
+
+	//Read file from DB
+	w := bytes.NewBuffer(make([]byte, 0))
+	_, getFileError := dbBucket.DownloadToStreamByName(fileName, w)
+	if getFileError != nil {
+		return nil, getFileError
+	}
+
+	fileBytes := w.Bytes()
+
+	//Return bytes
+	return fileBytes, nil
+
+}
+
+//GetDBInstance - Gets database intance
+func GetDBInstance(serverIPAddress, port, dbName string, timeOutInSeconds int) (*mongo.Database, error) {
+
+	serverIPAddress = strings.TrimSpace(serverIPAddress)
+	dbName = strings.TrimSpace(dbName)
+	port = strings.TrimSpace(port)
+
+	//Validations
+	if serverIPAddress == "" {
+		return nil, errors.New("serverIPAddress required")
+	} else if dbName == "" {
+		return nil, errors.New("dbName required")
+	} else if timeOutInSeconds <= 0 {
+		return nil, errors.New("valid timeOutInSeconds required")
+	}
+
+	ipElements := strings.Split(serverIPAddress, ".")
+	if len(ipElements) != 4 {
+		return nil, errors.New("invalid serverIPAddress")
+	}
+
+	if port == "" {
+		port = "27017"
+	}
+
+	//Connection string
+	connectionString := "mongodb://" + serverIPAddress + ":" + port
+	client, connectionError := mongo.NewClient(options.Client().ApplyURI(connectionString))
+	if connectionError != nil {
+		return nil, connectionError
+	}
+
+	//Context with timeout
+	ctx, _ := context.WithTimeout(context.Background(), time.Duration(timeOutInSeconds)*time.Second)
+	contextError := client.Connect(ctx)
+
+	if contextError != nil {
+		return nil, contextError
+	}
+
+	//Create a db instance
+	db := client.Database(dbName)
+
+	//Return db instance
+	return db, nil
+}